Summing Similar XML Elements for Display

Hello,

I have the following XML:

<?xml version="1.0" encoding="UTF-8"?>
<AccountsReceivable>
        <Payments CompanyCode="01" Payment="50"/>
        <Payments CompanyCode="02" Payment="100"/>
        <Payments CompanyCode="03" Payment="3000"/>
        <Payments CompanyCode="01" Payment="50"/>
        <Payments CompanyCode="02" Payment="200"/>
        <Payments CompanyCode="03" Payment="4000"/>
        <Payments CompanyCode="04" Payment="5"/>
        <Payments CompanyCode="01" Payment="50"/>
</AccountsReceivable>

What I need to do is sum all payment values that are associated with the
same company code for display.  I want the resulting XML to look something
like this:

<AccountsReceivable>
        <Payments CompanyCode="01" Payment="150"/>
        <Payments CompanyCode="02" Payment="300"/>
        <Payments CompanyCode="03" Payment="7000"/>
        <Payments CompanyCode="04" Payment="5"/>
</AccountsReceivable>

Can anyone offer me some suggestions?

Thanks,
Jim

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